BAUMANN FAMILY SCHOLARSHIP
2001 - 2002 Winners
Jaclyn Greimann and Kevin Spicka
Jaclyn Greimann and Kevin Spicka
Jaclyn Greimann's Research Proposal (November, 2001):
One of the most powerful tools in chemistry is the catalyst, which amplifies a reaction by lowering the activation energy of the reaction and allows the reactants to proceed to products at a greater rate. In biochemistry the enzyme accomplishes catalysis by three-dimensional conformational changes which often orientate its substrate(s) to a more favorable relation with the reactant(s). Stated more simply, the shape of an enzyme influences its function in catalysis. The definition of enzyme for many years has been a protein performing catalytic functions. It is now known that many ribonucleic acid molecules-naturally occurring in unicellular organisms-also perform physiological catalytic reactions. My research uses this finding and tweaks it a bit by investigating the catalytic activity of single stranded
deoxyribonucleic acid (DNA) molecules.
As I mentioned previously, the three-dimensional structure of an enzyme affects the catalytic function it performs. The same is true for the catalytic nucleic acids. Naturally DNA forms a double helix and the helical structure is non-catalytic. Via DNA synthesis we can define the base pairs of our single strand DNA molecule which can perform catalytic reactions in vitro. Little is known about the secondary interactions amongst the various bases in the single
strand DNA. Less is known about how these secondary structures lead to the functional tertiary structures.
I should note, however, that contrary to protein enzymes-which are true catalysts because they are neither permanently changed nor consumed during their reaction-catalytic nucleic acids are altered because the reactions they
perform are autocatalytic. The deoxyribozyme is both reactant and reaction enhancer. The deoxyribozyme I research is a self-kinasing enzyme. This means it adds a phosphate to the 5' end of the nucleic acid chain. The enzyme I research
somehow binds to an adenosine triphosphate (ATP) and takes the outermost (g) phosphate and adds it to the five prime end.
In order to "see" these microscopic reactions I react [g-P32] labeled ATP with our enzymatic nucleic acid. I run these radioactive pieces on a polyacrylamide gel and expose this gel to a screen specific to an instrument
called a phosphoimager which reads the radioactive particles on the screen. This gives Dr. Soukup and me an image similar to if we had exposed the gel to film, but as a computer file. In the near future my research will involve the
use of DNA base analogues which are DNA base pairs which contain an alteration to specific sites in the molecule. By inserting certain analogue base pairs in the structure of our enzyme we can then react the mutant strand with [g-P32]
labeled ATP and compare the reaction to that of the wild type strand. By knowing how mutant base pairs affect the reaction rate and where each mutant is located on the strand, we know which base pairs have a higher degree of
structural bonding, thus influencing catalysis. The ultimate idea behind nucleic acid enzymes is that once we have the ability to know which base pairs bond to others and their influence on the enzymatic reaction we can use this
knowledge to synthesize other catalytic DNA molecules to perform a variety of reactions.
Jaclyn Greimann's Research Report
Kevin Spicka's Research Proposal (November, 2001):
DNA-alkylating agents such as mitomycin C, CC-1065, and duocarmycins are used as
antitumor antibiotics, undergoing covalent bonding to AT-rich regions via 1,6 addition of a nucleophilic DNA moiety.
Research up to this point has yielded the molecule 3-phenylethynyl-2-cycloheptenone (1).
This molecule was then investigated to see if it undergoes a 1-6 conjugation addition, which it did. The molecule was prepared by expanding cyclopentanone to 1,3-cylcloheptadione by a 5+2 ring expansion method (scheme 1). After isolating the diketone, the scheme called for monoprotection as a monoenol ether, which called for converting the diketone to its enolate and then adding potassium t-butoxide mixed with isobutyl tosylate to give the desired enol ether. Upon treatment with phenylethynylmagnesium bromide in THF, the target molecule 1 was obtained.
Future proposed work.
Having successfully synthesized 1 and confirmed that it acts as a 1,6 addition substrate, it is now desired to see if this molecule can be converted the cyclopropanated 2. The bicycloketone 2 will be studied as a substrate for 1,6 addition reactions mimicking the CPI antibiotics as well as a synthon for entry into one-carbon, medium ring homologation chemistry.
7. Plans for presentation of research results (conference, publication, seminar, etc.)
Plans to present this research include a presentation at the Nebraska Academy of Sciences, as well as subsequent publication in Organic Letters.
Kevin Spicka's Research Report
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